On 28-May-06 Wayne Stallwood wrote:
On Sat, 2006-05-27 at 18:04 +0100, Ted.Harding@nessie.mcc.ac.uk wrote:
I thought of that, but couldn't see one anywhere. However, a little while ago, looking over the mother board I saw a block-like item attached to it, and guessing that this might be the clock I gave it a firm press with my thumb. Since then, the HW clock seems to be staying in sync with the system time (to a second or two), so maybe I've cured it!
The black box is a small "cap" over a socketed Real Time Clock chip (usually a Dallas) the cap contains a small 3 volt battery which is soldered to two of the chip legs that have been bent upwards. You are supposed to replace the device whole, but some of them are getting a bit hard to find, in which case you have to carefully prise of the top and replace the battery.
Just to slightly complicate matters. These devices contain a battery backed area of CMOS memory for the Bios configuration settings (not the BIOS itself that's on an EEPROM) Some systems need this Ram preloaded with some information before they will save to it. So on certain mainboards if you change the device or change the battery the BIOS will be unable to save it's configuration data and will run with defaults every time you boot the system.
Many thanks for all this info, Wayne. Unsuspected by me! It's good to learn by being told by an expert that's it's something I'm better off not fiddling with, rather than finding out the hard way. (Still keeping good time, by the way ... ).
In your case however I am not sure why pressing on it has cleared the fault. I think there may be a write enable pin, perhaps if this isn't connected properly the system cannot update the HW clock ?
In the words of an historic invoice from a maintenance engineer who, called in to fix a flaky box, gave it a thump on the side and got it working instantly:
To: Hitting the box . . . . . . . . £ 0.02 To: Knowing where to hit it . . . . £49.98 ------ TOTAL £50.00 ======
(Just my 2p-worth)
Cheers, Ted.
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